Various embodiments of the present invention relate to sensors and measurement devices, and more specifically, to pressure sensors.
There are a number of different pressure related parameters that can be measured. An absolute pressure sensor measures pressure relative to perfect vacuum pressure of 0 pounds per square inch (PSI) or zero pressure. Atmospheric pressure is 101.325 kPa (14.7 PSI) at sea level with reference to vacuum. The pressure measurement taken on a car tire is sometimes called gauge pressure. A gauge pressure sensor measures the pressure relative to a given atmospheric pressure at the location of the measurement. For example, when the tire pressure gauge reads 0 PSI, there is actually around 14.7 PSI (or atmospheric pressure) in the tire. A third type of pressure measurement is differential pressure. A differential pressure sensor measures the difference between two pressure inputs to the sensing device. For example, a differential pressure sensor could be used to measure the pressure increase across an oil pipeline pump.
There are several conventional designs for pressure sensors operating on the basis of a number of different technologies. Piezoresistive strain gauge pressure sensors exploit the piezoresistive effect to detect strain due to pressure applied to a bonded strain gauge. A piezoelectric pressure sensor uses the piezoelectric effect of materials such as quartz to measure pressure induced strain. A capacitive pressure sensor has a diaphragm and pressure cavity designed to create a variable capacitor for detecting strain due to applied pressure. Electromagnetic pressure sensors measure the displacement of a diaphragm by exploiting changes in inductance, the Hall Effect, the eddy current principal, or using a Linear Variable Differential Transformer (LVDT).
However, such conventional pressure sensing technologies are not well suited to measuring low differential pressures, are expensive, and may be difficult to operate in a environments which require high withstand pressures. Accordingly, a robust, compact pressure sensor suitable for measuring low differential pressures is needed.